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MR1888550 (2002k:90061) Galbiati, Giulia On the approximation of the minimum disturbance $p$-facility location problem. Third ALIO-EURO Meeting on Applied Combinatorial Optimization (Erice, 1999). Discrete Appl. Math. 118 (2002), no. 1-2, 73--83. (Reviewer: Sandra L. Arlinghaus) 90B80 (90C27)